JP3400525B2 - Method for manufacturing semiconductor device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention selectively selects fine patterns.
The present invention relates to a method of manufacturing a semiconductor device that can be formed
It

[0002]

2. Description of the Related Art In recent years, elements are becoming finer, and further finer lithography techniques are required. In particular, the hole pattern is more difficult to be miniaturized than the wiring pattern due to the resolution characteristics of the stepper, and the miniaturization technology is being developed. As a method of miniaturizing the hole and groove pattern, as described in JP-A-1-307228, after forming a resist pattern, heat treatment is performed at a temperature equal to or higher than the softening point of the resist, and the pattern is formed by thermal flow of the resist. There is a way to reduce it. However, in this method, the entire resist pattern of the entire wafer is heat-fluidized, so that the unnecessary pattern is reduced,
There were problems such as being crushed depending on the pattern.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for selectively forming fine hole and groove patterns by pattern deformation due to thermal flow of a resist without changing the design of a pattern transfer photomask. To provide.

[0004]

In order to achieve the above object, the present invention uses a photomask having a semi-transparent film around a transparent pattern on a photomask for pattern transfer corresponding to a pattern to be reduced, and exposure and development are performed. After that, the unexposed resist is not softened, and is heat-treated at a temperature at which the exposed resist is softened to selectively soften and flow a desired pattern.

[0005]

[Operation] By making the transparent pattern periphery on the photomask for pattern transfer corresponding to the pattern to be reduced semi-transparent,
The light transmitted through the semitransparent film decomposes part of the dissolution inhibitor in the resist around the pattern. As a result, the softening point temperature becomes lower than that of the unexposed resist, and the viscosity of the resist becomes smaller, so that heat flow easily occurs. By subjecting this to heat treatment, selective reduction of the desired pattern can be realized.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a photomask of the present invention. The figure (a) is a top view of a photomask, and the figure (b) is a sectional view of a photomask. 1 is a glass substrate, 2 is a light-shielding film,
3 is a semitransparent film. Here, the light shielding film 2 and the semitransparent film 3 are Cr films, and the transmissivity T of the semitransparent film 3 is 50%.
Further, the semi-transparent film 3 may be formed around the transparent pattern 6 by an experiment so that the width W is 0.2 μm or more from the edge of the transparent pattern, and here it is set to 1.0 μm.

The above mask was prepared by using lithography twice and processing the patterns of the transparent portions 6 and 7 the first time and the semi-transparent portion the second time. Here, the semitransparent control was performed by controlling the etching depth of the light shielding film 2. This method is not limited to this. For example, the light-shielding film is etched in the third, sixth, and seventh portions by the first lithography, the semi-transparent film is deposited on the entire surface, and then the third portion is half-etched by the second lithography. You may process so that a transparent film may remain. Although Cr was used for the semitransparent film, CrO, CrON, MoSiO, MoS
A translucent film such as iON may be used. Further, if the condition is such that the phase difference between the light passing through the semitransparent portion and the transparent portion is 180 °, the resolution characteristic of the pattern is also improved.

FIG. 2 shows the principle of the pattern forming method according to the present invention. FIG. 3A shows the photomask shown in FIG. By using this photomask by ordinary lithography, a substrate 5 to be processed as shown in FIG. 1B, which is coated with a resist 5, is exposed at a normal exposure amount or more,
Development was carried out with a developing solution having a normal development time or shorter or a normal concentration or lower to form a resist pattern as shown in FIG. Here, in the photomask for pattern transfer, the transfer patterns 8 and 9 of the transparent pattern 6 having a semi-transparent film in the periphery and the transparent pattern 7 having a light-shielding film in the periphery had substantially the same dimension D.

Next, as shown in FIG. 3D, the resist was heat-treated together with the substrate to be processed in a baking oven at a temperature not higher than the softening point of the unexposed portion resist.

By performing this heat treatment, the dimension D2 of the transfer pattern 9 of the transparent pattern 7 having a light shielding film in the periphery in the photomask for pattern transfer is determined because the resist around the transfer pattern 9 is not exposed. At temperatures below the softening point of the unexposed area resist, there is no thermal flow of the resist,
It does not change from the dimension D before heat treatment. On the other hand, in the transfer pattern 8 of the transparent pattern 6 in which the periphery of the pattern transfer photomask is a semitransparent film, the exposure portion 10 is exposed to the resist around the transfer pattern 8 by the light transmitted through the semitransparent film around the transparent pattern. It is formed. Part of the dissolution inhibitor in the resist of the exposed area 10 is decomposed, resulting in a lower softening point temperature and a lower viscosity of the resist. As a result, the exposure unit 10
Of the transfer pattern 8 is deformed by the flow of the resist in the exposed portion 10, and as a result, the dimension D1 of the transfer pattern 8 is the same as that before the heat treatment. The transfer pattern size D is less than or equal to D. Therefore, only a desired pattern can be reduced by heat flow by selecting a translucent film or a light-shielding film around the transparent pattern of the pattern transfer photomask.

FIG. 3 shows the relationship between the exposure amount of the exposed portion 10 by the light transmitted through the semitransparent film 3 in the pattern transfer photomask and the dimensions D1 and D2 of the transfer patterns 8 and 9 after the heat treatment. Here, a novolac-based resist is applied to the resist 5 with a resist film thickness of 1.0 μm, and the transmissivity T of the semitransparent film 3 is 5 μm.
After exposing and developing using a 0% pattern transfer photomask, a heat treatment for the purpose of reducing the pattern by softening flow of the resist was performed in a baking furnace at a heat treatment temperature of 120 ° C. for 180 seconds. The transfer pattern dimension D before heat treatment is 0.45 μm.

Exposure unit 10 by light transmitted through the semitransparent film 3
The amount of exposure is 50 mJ / sq cm ² or more resist pattern dimension is changed initially in the dimensions at 300 mJ / cm ² or more was hardly changed. When exposure was performed with an exposure amount of 620 mJ / cm ² using the pattern transfer photomask, the dimension D1 of the transfer pattern 8 of the transparent pattern 6 having a semitransparent film in the periphery of the pattern transfer photomask was 0.38 μm. Therefore, the object can be achieved by setting the transmittance T of the semitransparent film 3 and the total exposure amount so that the exposure amount of the exposed portion 10 by the light transmitted through the semitransparent film 3 becomes 50 mJ / cm ² or more.

Under the above heat treatment conditions, the dimension D2 of the transfer pattern 9 of the pattern 7 having the light-shielding film around the transparent pattern of the pattern transfer photomask does not change from that before the heat treatment. Therefore, the semitransparent film is formed on the pattern transfer photomask. By arranging, it becomes possible to selectively heat-flow the resist only in the desired pattern, and the pattern can be selectively reduced.

Here, the heat treatment temperature and heat treatment time for reducing the pattern by softening flow of the resist, the transmissivity and the pattern size and shape of the semitransparent film of the pattern transfer photomask are limited as described above. However, it is not limited to this. Further, the heat treatment temperature for the purpose of reducing the pattern by the softening flow of the resist is set to a temperature equal to or lower than the softening point of the unexposed portion resist, but the pattern can be reduced at a temperature equal to or higher than the softening point. In this case, the fact that the degree of flow differs between the two is used.

Although a resist containing a positive novolac resin as a main component is used as the resist 5, the present invention is not limited to this. Any material can be used as long as it is a material which causes heat flow and whose softening point is lowered by light irradiation.
The temperature at which the unexposed portion of the novolac-based resist used here causes thermal flow was 130 ° C. or higher.

Further, the conditions such as the transmissivity of the semitransparent film were set so that the above effect can be obtained by one exposure using the translucent film of the pattern transfer photomask arranged on the photomask. Select a desired pattern in the same manner even if you perform a heat treatment similar to the above conditions after forming a pattern using a normal pattern transfer photomask using a photomask with a transparent pattern in the same arrangement as above It goes without saying that it can be reduced. The planar shape of the reduced pattern is a hole pattern or a groove pattern, but is not limited to this. Although the hole pattern is a square here, the hole pattern is not limited to this, and may be a circle, an ellipse, a polygon such as a triangle or a pentagon.

When a pattern transfer photomask was used to form the electrode extraction hole pattern of the VLSI by this method, only a desired pattern could be selectively reduced, and higher density wiring could be realized. .

[0018]

By applying the present invention, a fine pattern exceeding the resolution limit can be selectively formed by a simple process.
In particular, it is possible to realize selective miniaturization of the electrode extraction hole pattern of the VLSI, which is difficult to miniaturize, and to realize the VLSI production using optical lithography, which is extremely advantageous industrially.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a manufacturing process according to an embodiment of the present invention.

FIG. 3 is an explanatory view of various embodiments of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Glass substrate, 2 ... Light-shielding film, 3 ... Semi-transparent film, 4 ... Processed substrate, 5 ... Resist, 6 ... Transparent pattern whose periphery is a semi-transparent film, 7 ... Transparent pattern whose periphery is a light-shielding film, 8 ... Transfer pattern of transparent pattern having a semi-transparent film in the periphery, 9 ... Transfer pattern of transparent pattern having a light-shielding film in the periphery, 10 ... Exposure part by light transmitted through the semi-transparent film.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor ▲ Hiroshi Takagi 5-20-1 Kamisuihonmachi, Kodaira-shi, Tokyo Inside Hitachi Ultra LSI Engineering Co., Ltd. (56) References Special Kaihei 4-143765 (JP, A) JP-A 1-258419 (JP, A) JP-A 59-232418 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03F 1 / 00-1/16

Claims (3)

(57) [Claims] 1. A step of forming a resist layer on a semiconductor substrate, a semitransparent region, and a first opening provided in the semitransparent region.
And a light shielding area and a second opening provided in the light shielding area
Exposing the resist layer through a photomask having
And a step of developing the exposed resist layer to expose the first opening and
And the first opening pattern and the first opening pattern respectively corresponding to the second opening and the second opening.
Process of forming a resist pattern having a two-opening pattern
And then softening the resist layer around the first opening pattern.
And the resist layer around the second opening pattern is fluidized.
Heat treating the semiconductor substrate to prevent
A method of manufacturing a semiconductor device, comprising: 2. The method of manufacturing a semiconductor device according to claim 1, wherein the first opening is a hole pattern. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the second opening is a hole pattern.